磷输入对湿地土壤有机碳矿化及可溶性碳组分的影响

Effects of phosphorus enrichment on mineralization of organic carbon and contents of dissolved carbon in a freshwater marsh soil

采用室内培养试验,研究了土壤非淹水(土壤含水量为田间最大持水量60%)和淹水条件下,外源磷输入对沼泽湿地土壤有机碳矿化和土壤可溶性有机碳(DOC)及可溶性无机碳(DIC)含量的影响.结果表明,不同土壤水分条件下,土壤有机碳的矿化速率和累积矿化量均随着外源磷输入量的增加而增大;培养65d后,土壤DOC含量表现为先降低后升高,而DIC含量则逐渐增大.不同磷处理下土壤有机碳的累积矿化量与土壤DOC含量之间的相关关系并不显著,但是与土壤DIC含量之间呈显著的正相关关系[R为0.98(淹水),0.99(非淹水);P<0.05].相同磷输入水平下,淹水处理时土壤有机碳的累积矿化量、DOC和DIC含量均高于非淹水处理.外源磷输入沼泽湿地后,会通过提高土壤有机碳的矿化速率和土壤可溶性碳组分的淋失,加快土壤有机碳的损失速率及土壤CO2的排放量.

Based on the laboratory incubation experiment, the mineralization of soil organic carbon, contents of dissolved organic carbon （DOC） and dissolved inorganic carbon （DIC） with different phosphorus inputs, conditions, un-submerged （60% of the maximal water holding capacity, 60%WHC） and submerged were investigated. The mineralization rates and accumulative mineralization increased with P inputs under both soil water conditions. The contents of DOC decreased at first and then increased with the increase of P inputs, while the contents of DIC increased all the time after 65d of the incubation. There was no significant correlation between the accumulative mineralization of organic carbon and DOC, however, significant positive correlation were observed between the accumulative mineralization and contents of DIC [R=0.98（60%WHC）, 0.99（submerged）; P〈0.05]. Under the same P level, the accumulative mineralization of organic carbon and the contents of DOC and DIC under submerged condition were all higher than that at 60%WHC condition. Results also suggested that the increased inputs of P fertilizer might quicken the loss of soil organic carbon by largely enhancing the mineralization rates of organic carbon and the contents of dissolved carbon, and increased CO2 emission from the soil.